1. Field of the Invention
The present invention relates to a magnetic recording medium having a servo pattern formed of a concave/convex pattern in a servo pattern region, to a recording/reproducing apparatus having the magnetic recording medium, and to a stamper for manufacturing the magnetic recording medium.
2. Description of the Related Art
U.S. Pat. No. 5,772,905 discloses nanoimprint lithography (an imprint method of forming a concave/convex pattern of nanometer size: hereinafter, also called “imprint method”). According to the nanoimprint lithography, in a process of manufacturing semiconductor devices, information recording mediums, and the like, a concave/convex pattern of nanometer size is formed on a substrate by transferring a concave/convex shape of a stamper onto the substrate by pressing the stamper on which a concave/convex pattern of nanometer size is formed. In the imprint method described above, first, a stamper (mold) having a concave/convex pattern of nanometer size (as an example, a minimum width of about 25 nm) on a transfer surface is manufactured. Specifically, a resin layer is formed to cover a thin film (molding layer) of silicon oxide and the like formed on the silicon substrate, and a desired pattern is drawn on the resin layer using an electron beam lithography apparatus. Subsequently, the thin film is etched by a reactive ion etching apparatus using the resin layer as a mask, and a concave/convex pattern having a plurality of convex portions (features) is formed in the thickness of the thin film, thereby the stamper is manufactured.
Next, a resin layer (thin film layer) having a thickness of 55 nm is formed by spin coating polymethyl methacrylate (PMMA: resin material) on a surface of, for example, a silicon substrate. Subsequently, after both a laminated body, which is composed of the substrate and the resin layer, and the stamper are heated, the respective concave portions of the stamper are pressed against the resin layer on the substrate. At the time, since the resin material in the portions into which the convex portions of the stamper are forcibly inserted moves to the concave portions of the stamper, concave portions (regions) are formed (transferred) to the portions in which the convex portions are forcibly inserted. Next, after the laminated body against which the stamper is pressed is left as it is until the temperature thereof is lowered to a room temperature, the stamper is exfoliated from the resin layer. With this operation, the respective convex portions of the concave/convex pattern of the stamper are transferred onto the resin layer and a concave/convex pattern of nanometer size is formed on the substrate (resin layer). Subsequently, a substrate is etched using the resin layer on which the concave/convex pattern is formed as a mask, thereby a plurality of concave portions are formed on the substrate. Accordingly, when concave portions are formed on a resin layer of a substrate for an information recording medium by the above technology (imprint method), an information recording medium having a concave/convex pattern of nanometer size can be manufactured executing etching processing using the resin layer as a mask.